How are the relationships of elements in a group different from the relationships of elements in a period?
Elements in the main groups ( not transition elements) share the same number of valence electrons. Elements in the same period are filling the same energy level. Transition elements have empty orbitals that are able to accept extra elections under certain situations. One can see using the quantum theory the similarities, in groups and periods. Group 1 elements tend to have
Hydrogen's electron configuration is
Lithium's electron configuration is
Elements in the same period are adding an electron to the sublevel til it is full. Fluorine's configuration is
Neon's configuration is